Oreocharis oriolus, a new species of Gesneriaceae in a sclerophyllous oak community from Yunnan, Southwest China

Abstract Oreocharis oriolus, a new species of Gesneriaceae in a sclerophyllous oak community from Yunnan, Southwest China, is described and illustrated. Morphologically, it resembles both O. forrestii and O. georgei, while it is distinct in combined characters of wrinkled leaves, peduncle and pedicel covered with whitish and egladular villous hairs, bract lanceolate and nearly glabrescent adaxially, and staminode absent. Molecular phylogenetic analysis based on nuclear ribosomal internal transcribed spacer (nrITS) and chloroplast DNA fragment (trnL‐F) of 61 congeneric species also supported O. oriolus as a new species while it was nested with O. delavayi. It was currently assessed as ‘Critically Endangered’ (CR) regarding to its small‐sized population and narrow distribution following the IUCN categories and criteria.

Quite a few species in Oreocharis were found on cliffs or in crevices of mountainous areas, where it is usually difficult to access (Wang et al., 1990(Wang et al., , 1998. Recently, with explorations accessible to formerly remote regions, the accounts of this genus were constantly added (e.g., Cai et al., 2020;Du et al., 2021Du et al., , 2022Yang et al., 2017Yang et al., , 2019. During a field investigation on a sclerophyllous oak community (dominated by Quercus guyavifolia H.Lév.) in August 2021, we found an unknown species of Oreocharis in Ninglang County, North Yunnan Province. It matches the morphological commonalities of Oreocharis, with characters such as rosette habit, bilateral symmetrical flowers, four fertile stamens, and capsule loculicidal dehiscing into two valves right down the receptacle (see Table S1). It resembles both O. georgei Anthony (1934: 202) and O. forrestii (Diels) Skan (1917: t. 8719), but it fits neither of them with its unique characters, such as venation on leaves, indumentum of peduccle, pedicel and bract, and the shape of bract. It was confirmed to be a new species by our further literature perusal (Pan et al., 2019;Wang et al., 1998;Yang et al., 2017) and morphological comparison with herbarium specimens (physical and virtual specimens at BM, CDBI, E, FI, IBK, IBSC, K, KUN, P, PE, and US, acronym following Thiers, 2022). And it is thereafter named as O. oriolus. Phylogenetic analysis using mainly nuclear ribosome internal transcribed spacer (nrITS) and chloroplast DNA fragment (trnL-F) confirmed its position in this genus.

| Morphological description
The measurements and description of the new species, Oreocharis oriolus, were based on living plants in the field and the specimens at herbarium (CDBI & IBK), the morphological characters were measured using ImageJ v1.53k (Schneider et al., 2012) and are described using the terminology proposed by Harris and Harris (1994), Wang et al. (1998). Studied voucher specimens including the type materials and additional silica-gel dried leaves are stored at CDBI and IBK.

| DNA extraction, amplification, and sequencing
The sequences of the 67 species for molecular phylogenetic analysis were retrieved from GenBank (accessions referring to Table S2) (Table S2).

| Phylogenetic analyses
The sequences of the new species were processed using Sequencher v4.1.4 (Gene Codes, Ann Arbor, Michigan, USA) and aligned with all used sequences via MAFFT v7.475 (Katoh & Standley, 2013) with default parameters. The incongruence length difference test (ILD) was used to quantify the conflicts between nuclear DNA and plastid DNA data in PUPA v4.0a169 (Darlu & Lecointre, 2002;Swofford, 2002). Maximum likelihood (ML) and Bayesian inference (BI) methods were applied to infer the gene tree. jModeltest v2.1.6 (Posada, 2008) identified GTR+G as the best model for nrITS and trnL-F which selected using the corrected Akaike Information Criterion (AICc). BI analysis was conducted using MrBayes 3.2.7a (Ronquist & Huelsenbeck, 2003) with two parallel runs (10 million generations). The first 25% of the trees were discarded as burn-in, and the remaining trees were used to generate a majority-rule consensus tree. ML analysis was performed using IQ-TREE v1.4.241 (Nguyen et al., 2014), the ModelFinder in IQ-TREE tested a total of 286 DNA models and chose GTR+F+I+G4 as the best-fit nucleotide substitution model for the combined nrITS and trnL-F matrices, and branch support was estimated using 2000 replicates of ultrafast bootstrapping algorithm (UFboot) (Minh et al., 2013).

| RE SULTS
The ILD test (p = .6) showed that the plastid DNA (trnL-F) and nuclear DNA (nrITS) were highly congruent. The molecular phylogenetic tree showed that the 62 species of Oreocharis formed a well-supported monophyletic group (BI/ML = 1/100, Figure 1).

| Diagnosis
It is morphologically similar to Oreocharis forrestii, but it can be distinguished from the latter in bracts lanceolate (vs. linear to linearlanceolate) and adaxial surface glabrescent to nearly glabrous (vs. sparsely rust-brown villous or pubescent), pedicel sparsely brownish pubescent (vs. villous and glandular-pubescent), calyx lobes glabrescent to nearly glabrous on abaxial surfaces (vs. sparsely pubescent and glandular-puberulent), anthers ovate-triangle to nearly triangle (vs. broadly oblong).

| Phenology
Flowering in July and fruiting from August to November.

| Etymology
The brightly yellow flowers of this new species reminisced about the lively birds oriole (Oriolus oriolus), and the epithet is here used as a noun in apposition. Its Chinese name, Huáng Lí Mǎ Líng Jù Taí (黄鹂马 铃苣苔), is also taken this envision.

| Distribution and habitat
This new species is presently only known from type locality, North

| Conservation status
Apart from the subpopulation where we did the vegetation survey and the type specimen was collected, there are approximately 300 individuals confirmed restricted in an area of 2 km 2 (Figure 4). We also made extensive vegetation investigations in adjacent areas and failed to find this new species at similar habitats. It is temporarily assessed as Critically Endangered (CR B2ab (iii, v)) based on the IUCN

| Taxonomic affinities
The corolla of being campanulate tubular and the length of tube being about two times that of corolla limb showed that Oreocharis oriolus should be considered as a morphologically most related species of O. forrestii. And this new species also resembles O. georgei in dichotomous cyme with 4-10 flowers, in narrowly cylindrical corolla tube slightly constricted at throat while moderately inflated at base, in 2-lipped corolla limb equal to or slightly shorter than corolla tube in length, and in usually 2-sect adaxial lip and 3-sect abaxial lip with lobes oblong to oblong-lanceolate. A comparison of morphological characters of these three species are summarized in Table 1.

ACK N OWLED G M ENTS
We are grateful to Ms. Lin-Rui Wang and Ms. Feng Tang from Yibin University for their helps during the field works, and to Ms. Yu-Jie Chen (Hangzhou Botanical Garden) for preparing the line drawing.

FU N D I N G I N FO R M ATI O N
This study is jointly supported by the Second Tibetan Plateau

CO N FLI C T O F I NTER E S T S TATEM ENT
There is no conflict of interest to declare.